Method for improving antiwear performance and demulsibility performance

ABSTRACT

A method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition including a lubricating oil base stock as a major component, and an antiwear additive as a minor component. The antiwear additive includes a zinc dialkyl dithiophosphate compound represented by the formula 
       Zn[SP(S)(OR 1 )(OR 2 )] 2    
     wherein R 1  and R 2  are independently primary or secondary C 1  to C 8  alkyl groups. The R 1  and R 2  primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance. The lubricating oils of this disclosure are suitable for use in marine system oils for two-stroke marine diesel engines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 61/981,247 filed Apr. 18, 2014, which is herein incorporated by reference in its entirety.

FIELD

This disclosure relates to a method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil that has a particular ZDDP compound present in a particular amount in the formulated oil. The lubricating oils of this disclosure are useful in engine crankcases used in marine applications.

BACKGROUND

Engine designers are continually striving for more efficient engines that provide a better value to customers and last for a longer time period. As such, engine designs are becoming more severe and the need for improved antiwear protection is on the forefront.

In addition to antiwear, marine diesel engines have requirements for superior demulsibility to shed water from the lubricant. This allows the oil and the equipment to last longer by preventing poor lubricity, corrosion, and rust.

In particular, large 2-stroke marine diesel engines include an engine, a crankcase, and a propeller. System oils are commonly used to lubricate the crankcase of marine engines. Marine system oils tend to lose certain performance characteristics and benefits over time in marine environments. Marine system oils are particularly susceptible to performance deterioration due to the introduction of water into the marine crankcase. Normally water separates from oil, and in an engine or crankcase, should this not occur, the water will induce corrosion and lead to the hydrolysis of certain lubricant additives leading to acidic byproducts that attack the engine further.

Current load carrying FZG requirements from OEMs is set to a Failure Load Stage 11, but major OEMs are expected to increase the specification to a minimum Failure Load Stage 12 in new oils. Improved antiwear protection can be achieved by increasing the treat rate of zinc dialkyl dithiophosphate (ZDDP) antiwear additive, but typically at the cost of demulsibility performance. Current technologies cause demulsibility problems when the ZDDP antiwear additive treat rate is increased.

A major challenge in engine oil formulation is simultaneously achieving improved antiwear performance while also achieving improved demulsibility performance.

Despite the advances in lubricant oil formulation technology, there exists a need for an engine oil lubricant that effectively improves antiwear performance while also achieving improved demulsibility performance.

SUMMARY

This disclosure relates in part to a method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil that has a particular ZDDP compound present in a particular amount in the formulated oil. The lubricating oils of this disclosure are useful in marine engines, in particular, marine diesel engine system oil applications including the gears of two-cycle or four-cycle marine engines.

This disclosure also relates in part to a method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition comprising a lubricating oil base stock as a major component, and an antiwear additive as a minor component. The antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula

Zn[SP(S)(OR¹)(OR²)]₂

wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups. The R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil.

This disclosure further relates in part to a lubricating engine oil having a composition comprising a lubricating oil base stock as a major component, and an antiwear additive as a minor component. The antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula

Zn[SP(S)(OR¹)(OR²)]₂

wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups. The R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil, are sufficient for the lubricating engine oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil.

It has been surprisingly found that, in accordance with this disclosure, improvements in antiwear performance and demulsibility performance are obtained in an engine lubricated with a lubricating oil, by including a particular ZDDP compound present in a particular amount, in the lubricating oil. The ZDDP compound is, preferably, the zinc dialkyl dithiophosphate compound having primary or secondary alkyl groups that are derived from an alcohol selected from 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-hexanol, 2-ethyl-2-hexanol, or mixtures thereof. The lubricating oils of this disclosure are suitable for use in marine system oil applications. As an example, the lubricating oils described herein may be suitable to lubricate the bearings, gears, and hydraulics lubricated by the system oil of two-stroke crosshead marine diesel engines.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows formulation details in weight percent based on the total weight percent of the formulation, of various lubricating oil formulations. FIG. 1B shows the results of testing for kinematic viscosity (KV) at 100° C. measured by ASTM D445, elemental analysis of lubricating oils measured by ASTM D4951, antiwear of the lubricating oils measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG (i.e., FZG Failure Load Stage, determined by observing gears at increasing load levels until scuffing is noticed on the gear face), and demulsibility of the lubricating oils measured by High Shear Demulsibility Test as described herein.

FIGS. 2A and 2B detail which ZDDP was used in the lubricating oil blends in each of the examples given in FIGS. 3-19. The general formula used in the lubricating oil blends in all examples in FIGS. 3-19 is approximately 96-97 weight % base oil, approximately 0-1 weight % ZDDP, and approximately 3% other additives. The only varying component in the lubricating oil blends is the ZDDP component (weight %) for both FIGS. 2A and 2B.

FIG. 3 graphically shows the results of demulsibility testing of the lubricating oil measured by the High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 4 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 5 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 6 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 7 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 8 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 9 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 10 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 11 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 12 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 13 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 14 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 15 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 16 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 17 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 18 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 19 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The lubricating oil blends used in the Examples are described in FIGS. 1, 2A, and 2B.

FIG. 20 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples.

FIG. 21 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples.

FIG. 22 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples.

FIG. 23 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

It has now been found that improved antiwear performance and demulsibility performance can be attained in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil that has a particular ZDDP compound present in a particular amount in the formulated oil. The formulated oil preferably comprises a lubricating oil base stock as a major component, and a particular ZDDP compound as minor component. The lubricating oils of this disclosure are particularly advantageous as marine crankcase system oils.

The lubricating oils of this disclosure provide excellent engine protection including anti-wear performance and demulsibility performance. This benefit has been demonstrated for the lubricating oils of this disclosure in antiwear measurements of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test as described herein.

In antiwear measurements of the lubricating oils of this disclosure as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance is improved as compared to the antiwear performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups of this disclosure, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oils of this disclosure.

Demulsibility measurements of the lubricating oils of this disclosure were measured by High Shear Demulsibility Test. This method is conducted by taking a sample of oil and adding 5% water to a graduated container, then mixing at over 10,000 RPM for less than 2 minutes. The mixture is then separated by centrifuge at over 500 G's for 2 hours. Water, oil, and emulsion layers are measured in mL visually after the test. Water in oil can be determined by Karl Fischer method, ASTM E203. A lower result for emulsion, preferably below 1 mL, and lower water in oil, preferably below 1 wt %, is desirable, while a higher result for free water, preferably above 3.8 mL, is preferred. The demulsibility performance is unexpectedly improved as compared to the demulsibility performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups of this disclosure, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oils of this disclosure.

The lubricating oils of this disclosure useful for marine crankcase systems provide improved FZG load carrying capability without sacrificing demulsibility performance. Historically, the ZDDP antiwear additive used to improve FZG load carrying performance has shown poorer demulsibility performance with increasing treat rates. In accordance with this disclosure, it is shown that by adjusting the ZDDP alcohol chain length used in the lubricating oil formulations, optimum demulsibility performance can be obtained, even at higher treat rates. For longer alcohol chains such as primary C8, secondary i-C6, or primary or iso-C5 types the treat rate is in the 0.1 to 0.8 weight percent range, preferably from about 0.2 to about 0.8 weight percent, and more preferably from about 0.2 to about 0.6 weight percent. Shorter chains such as secondary iso-C3 or 2-C4 types show good demulsibility performance at about 0.3 to about 0.8 weight percent range, preferably from about 0.4 to about 0.8 weight percent, or more preferably from about 0.4 to about 0.7 weight percent. In accordance with this disclosure, longer chain ZDDP additives were unexpectedly better for demulsibility performance and shorter chain ZDDP additives were better for FZG performance. This disclosure achieves superior performance in both FZG load carrying capability and demulsibility through the use of these alcohols chains in the manufacture of ZDDP.

As used herein, the term “marine” is intended to encompass any body of water including saltwater and/or fresh water environments.

Lubricating Oil Base Stocks

A wide range of lubricating base oils is known in the art. Lubricating base oils that are useful in the present disclosure are both natural oils, and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between about 80 to 120 and contain greater than about 0.03% sulfur and/or less than about 90% saturates. Group II base stocks have a viscosity index of between about 80 to 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than about 120 and contain less than or equal to about 0.03% sulfur and greater than about 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or >0.03% and ≧80 and <120 Group II ≧90 and ≦0.03% and ≧80 and <120 Group III ≧90 and ≦0.03% and ≧120 Group IV Includes polyalphaolefins (PAO) products Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked basestocks, and/or synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters are also well known basestock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks are commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are known materials and generally available on a major commercial scale from suppliers such as ExxonMobil Chemical Company, Chevron Phillips Chemical Company, BP, and others, typically vary from about 250 to about 5,000, although PAO's may be made in viscosities up to about 1000 cSt (100° C.). The PAOs are typically comprised of relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include, but are not limited to, C₂ to about C₃₂ alphaolefins with the C₆ to about C₁₆ alphaolefins, such as 1-hexene, 1-octene, 1-decene, 1-dodecene and the like, being preferred. The preferred polyalphaolefins are poly-1-hexene, poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures thereof and mixed olefin-derived polyolefins. However, the dimers of higher olefins in the range of C₁₄ to C₁₈ may be used to provide low viscosity base stocks of acceptably low volatility. Depending on the viscosity grade and the starting oligomer, the PAOs may be predominantly trimers and tetramers of the starting olefins, with minor amounts of the higher oligomers, having a viscosity range of 1.5 to 1000 cSt or more. PAO fluids of particular use may include 3.0 cSt, 3.4 cSt, 3.6 cSt, 4 cSt, 6 cSt, 8 cSt, 10 cSt, 40 cSt, 100 cSt, and/or 150 cSt, and combinations thereof.

The PAO fluids may be conveniently made by the polymerization of an alphaolefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate. For example the methods disclosed by U.S. Pat. Nos. 4,149,178 or 3,382,291 may be conveniently used herein. Other descriptions of PAO synthesis are found in the following U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No. 4,218,330.

Other useful lubricant oil base stocks include wax isomerate base stocks and base oils, comprising hydroisomerized waxy stocks (e.g. waxy stocks such as gas oils, slack waxes, fuels hydrocracker bottoms, etc.), hydroisomerized Fischer-Tropsch waxes, Gas-to-Liquids (GTL) base stocks and base oils, and other wax isomerate hydroisomerized base stocks and base oils, or mixtures thereof Fischer-Tropsch waxes, the high boiling point residues of Fischer-Tropsch synthesis, are highly paraffinic hydrocarbons with very low sulfur content. The hydroprocessing used for the production of such base stocks may use an amorphous hydrocracking/hydroisomerization catalyst, such as one of the specialized lube hydrocracking (LHDC) catalysts or a crystalline hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst. For example, one useful catalyst is ZSM-48 as described in U.S. Pat. No. 5,075,269, the disclosure of which is incorporated herein by reference in its entirety. Processes for making hydrocracked/hydroisomerized distillates and hydrocracked/hydroisomerized waxes are described, for example, in U.S. Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as in British Patent Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Each of the aforementioned patents is incorporated herein in their entirety. Particularly favorable processes are described in European Patent Application Nos. 464546 and 464547, also incorporated herein by reference. Processes using Fischer-Tropsch wax feeds are described in U.S. Pat. Nos. 4,594,172 and 4,943,672, the disclosures of which are incorporated herein by reference in their entirety.

Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized (wax isomerate) base oils may be advantageously used in the instant disclosure, and may have useful kinematic viscosities at 100° C. of about 3 cSt to about 50 cSt, preferably about 3 cSt to about 30 cSt, more preferably about 3.5 cSt to about 25 cSt, as exemplified by GTL 4 with kinematic viscosity of about 4.0 cSt at 100° C. and a viscosity index of about 141. These Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized base oils may have useful pour points of about −20° C. or lower, and under some conditions may have advantageous pour points of about −25° C. or lower, with useful pour points of about −30° C. to about −40° C. or lower. Useful compositions of Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and wax-derived hydroisomerized base oils are recited in U.S. Pat. Nos. 6,080,301; 6,090,989, and 6,165,949 for example, and are incorporated herein in their entirety by reference.

The hydrocarbyl aromatics can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatic can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from about C₆ up to about C₆₀ with a range of about C₈ to about C₂₀ often being preferred. A mixture of hydrocarbyl groups is often preferred, and up to about three such substituents may be present. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 3 cSt to about 50 cSt are preferred, with viscosities of approximately 3.4 cSt to about 20 cSt often being more preferred for the hydrocarbyl aromatic component. An alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene can be used. Other alkylates of aromatics can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be about 2% to about 25%, preferably about 4% to about 20%, and more preferably about 4% to about 15%, depending on the application.

Alkylated aromatics such as the hydrocarbyl aromatics of the present disclosure may be produced by well-known Friedel-Crafts alkylation of aromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York, 1963. For example, an aromatic compound, such as benzene or naphthalene, is alkylated by an olefin, alkyl halide or alcohol in the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many homogeneous or heterogeneous, solid catalysts are known to one skilled in the art. The choice of catalyst depends on the reactivity of the starting materials and product quality requirements. For example, strong acids such as AlCl₃, BF₃, or HF may be used. In some cases, milder catalysts such as FeCl₃ or SnCl₄ are preferred. Newer alkylation technology uses zeolites or solid super acids.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols (such as the neopentyl polyols, e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol) with alkanoic acids containing at least about 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Suitable synthetic ester components include the esters of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids containing from about 5 to about 100 carbon atoms. These esters are widely available commercially, for example, the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company.

Also useful are esters derived from renewable material such as coconut, palm, rapeseed, soy, sunflower and the like. These esters may be monoesters, di-esters, polyol esters, complex esters, or mixtures thereof. These esters are widely available commercially, for example, the Mobil P-51 ester of ExxonMobil Chemical Company.

Engine oil formulations containing renewable esters are included in this disclosure. For such formulations, the renewable content of the ester is typically greater than about 70 weight percent, preferably more than about 80 weight percent and most preferably more than about 90 weight percent.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non-conventional or unconventional base stocks/base oils include one or more of a mixture of base stock(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate base stock(s) derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from about 2 mm²/s to about 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to about −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of about 80 to about 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than about 10 ppm, and more typically less than about 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) and hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than about 10 ppm, and more typically less than about 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this material especially suitable for the formulation of low sulfur, sulfated ash, and phosphorus (low SAP) products.

Base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

The base oil constitutes the major component of the engine oil lubricant composition of the present disclosure and typically is present in an amount ranging from about 50 to about 99 weight percent, preferably from about 70 to about 98 weight percent, and more preferably from about 85 to about 98 weight percent, based on the total weight of the composition. The base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricating oils for spark-ignited and compression-ignited engines. The base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 2.5 cSt to about 12 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 9 cSt (or mm²/s) at 100° C. Mixtures of synthetic and natural base oils may be used if desired.

Antiwear Additive

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) is a useful component of the lubricating oils of this disclosure. ZDDP can be derived from primary alcohols, secondary alcohols or mixtures thereof. The preferred ZDDP compounds generally are represented by the formula

Zn[SP(S)(OR¹)(OR²)]₂

wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups. The R¹ and R² substituents can independently be C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched. Alkyl aryl groups may also be used.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.

Preferably, the primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-hexanol, or mixtures thereof.

The R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups.

In general, the ZDDP can be used in amounts of from about 0.2 weight percent to about 1.2 weight percent, preferably from about 0.3 weight percent to about 1.0 weight percent, more preferably from about 0.4 weight percent to about 0.8 weight percent, still more preferably from about 0.4 weight percent to about 0.7 weight percent, and even still more preferably from about 0.4 weight percent to about 0.6 weight percent, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a primary, secondary or mixture ZDDP and present in an amount of from about 0.4 to 1.0 weight percent of the total weight of the lubricating oil.

Preferably, the zinc dialkyl dithiophosphate compounds having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, are present in an amount of from about 0.1 weight percent to about 1.0 weight percent, preferably from about 0.2 weight percent to about 0.8 weight percent, more preferably from about 0.4 weight percent to about 0.8 weight percent, still more preferably from about 0.4 weight percent to about 0.7 weight percent, and even more preferably from about 0.4 weight percent to about 0.6 weight percent, based on the total weight of the lubricating oil.

Preferably, the zinc dialkyl dithiophosphate compounds having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, are present in an amount of from about 0.1 weight percent to about 1.0 weight percent, preferably from about 0.2 weight percent to about 0.8 weight percent, more preferably from about 0.3 weight percent to about 0.8 weight percent, still more preferably from about 0.3 weight percent to about 0.7 weight percent, and even more preferably from about 0.4 weight percent to about 0.7 weight percent, or even more preferably from about 0.4 weight percent to about 0.6 weight percent, based on the total weight of the lubricating oil.

Preferably, the zinc dialkyl dithiophosphate compounds having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, are present in an amount of from about 0.3 weight percent to about 1.0 weight percent, preferably from about 0.3 weight percent to about 0.8 weight percent, more preferably from about 0.3 weight percent to about 0.7 weight percent, still more preferably from about 0.3 weight percent to about 0.6 weight percent, and even more preferably from about 0.4 weight percent to about 0.6 weight percent, based on the total weight of the lubricating oil.

Other Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to antiwear agents, dispersants, other detergents, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N.J. (1973); see also U.S. Pat. No. 7,704,930, the disclosure of which is incorporated herein in its entirety. These additives are commonly delivered with varying amounts of diluent oil, that may range from 5 weight percent to 50 weight percent.

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

Viscosity Index Improvers

Viscosity index improvers (also known as VI improvers, viscosity modifiers, and viscosity improvers) can be included in the lubricant compositions of this disclosure.

Viscosity index improvers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity index improvers include high molecular weight hydrocarbons, polyesters and viscosity index improver dispersants that function as both a viscosity index improver and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,500,000, more typically about 20,000 to 1,200,000, and even more typically between about 50,000 and 1,000,000.

Examples of suitable viscosity index improvers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity index improver. Another suitable viscosity index improver is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity index improvers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers, are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 5850B”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Polyisoprene polymers are commercially available from Infineum International Limited, e.g. under the trade designation “SV200”; diene-styrene copolymers are commercially available from Infineum International Limited, e.g. under the trade designation “SV 260”.

The viscosity index improvers may be used in an amount of less than about 2.0 weight percent, preferably less than about 1.0 weight percent, and more preferably less than about 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil. Viscosity improvers are typically added as concentrates, in large amounts of diluent oil.

The viscosity index improvers may be used in an amount of from 0.25 to about 2.0 weight percent, preferably 0.15 to about 1.0 weight percent, and more preferably 0.05 to about 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil.

Detergents

Illustrative detergents useful in this disclosure include, for example, alkali metal detergents, alkaline earth metal detergents, or mixtures of one or more alkali metal detergents and one or more alkaline earth metal detergents. A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur acid, carboxylic acid, phosphorous acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal.

Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Mildly overbased detergents have a TBN of from 80 to 200 and highly overbased detergents have a TBN of 200 or greater. Useful detergents can be neutral, mildly overbased, or highly overbased. These detergents can be used in mixtures of neutral, overbased, highly overbased calcium salicylate, sulfonates, phenates and/or magnesium salicylate, sulfonates, phenates. The TBN ranges can vary from low, medium to high TBN products, including as low as 0 to as high as 600. Mixtures of low, medium, high TBN can be used, along with mixtures of calcium and magnesium metal based detergents, and including sulfonates, phenates, salicylates, and carboxylates. A detergent mixture with a metal ratio of 1, in conjunction of a detergent with a metal ratio of 2, and as high as a detergent with a metal ratio of 5, can be used. Borated detergents can also be used.

Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀ or mixtures thereof. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched and can be used from 0.5 to 6 weight percent. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.

Metal salts of carboxylic acids are also useful as detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula

where R is an alkyl group having 1 to 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, or barium. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.

Alkaline earth metal phosphates are also used as detergents and are known in the art.

Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.

Preferred detergents include calcium phenates, calcium sulfonates, calcium salicylates, magnesium phenates, magnesium sulfonates, magnesium salicylates and other related components (including borated detergents), and mixtures thereof. Preferred mixtures of detergents include magnesium sulfonate and calcium salicylate, magnesium sulfonate and calcium sulfonate, magnesium sulfonate and calcium phenate, calcium phenate and calcium salicylate, calcium phenate and calcium sulfonate, calcium phenate and magnesium salicylate, calcium phenate and magnesium phenate.

The detergent concentration in the lubricating oils of this disclosure can range from 1.0 to 6.0 weight percent, preferably 2.0 to 5.0 weight percent, and more preferably from 2.0 weight percent to 4.0 weight percent, based on the total weight of the lubricating oil.

As used herein, the detergent concentrations are given on an “as delivered” basis. Typically, the active detergent is delivered with a process oil. The “as delivered” detergent typically contains from 20 weight percent to 80 weight percent, or from 40 weight percent to 60 weight percent, of active detergent in the “as delivered” detergent product. The use of detergent may be beneficial when combined with ZDDP.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful, although on occasion, having a hydrocarbon substituent between 20-50 carbon atoms can be useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from 1:1 to 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500 or more. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid and cyclic carbonate. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from 0.1 to 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HNR₂ group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides, or mixtures of borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from 500 to 5000, or from 1000 to 3000, or 1000 to 2000, or a mixture of such hydrocarbylene groups, often with high terminal vinylic groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components. Such additives may be used in an amount of 0.1 to 20 weight percent, preferably 0.5 to 8 weight percent, or more preferably 0.5 to 4 weight percent. On an active ingredient basis, such additives may be used in an amount of 0.06 to 14 weight percent, preferably 0.3 to 6 weight percent. The hydrocarbon portion of the dispersant atoms can range from C60 to C400, or from C70 to C300, or from C70 to C200. These dispersants may contain both neutral and basic nitrogen, and mixtures of both. Dispersants can be end-capped by borates and/or cyclic carbonates.

As used herein, the dispersant concentrations are given on an “as delivered” basis. Typically, the active dispersant is delivered with a process oil. The “as delivered” dispersant typically contains from about 20 weight percent to about 80 weight percent, or from about 40 weight percent to about 60 weight percent, of active dispersant in the “as delivered” dispersant product.

Antioxidants

Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.

Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C₆+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant disclosure. Examples of ortho-coupled phenols include: 2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol); and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4′-bis(2,6-di-t-butyl phenol) and 4,4′-methylene-bis(2,6-di-t-butyl phenol).

Effective amounts of one or more catalytic antioxidants may also be used. The catalytic antioxidants comprise an effective amount of a) one or more oil soluble polymetal organic compounds; and, effective amounts of b) one or more substituted N,N′-diaryl-o-phenylenediamine compounds or c) one or more hindered phenol compounds; or a combination of both b) and c). Catalytic antioxidants are more fully described in U.S. Pat. No. 8,048,833, herein incorporated by reference in its entirety.

Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(X)R¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, and preferably contains from 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of at least 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alphanaphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alphanaphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another. Such additives may be used in an amount of 0.01 to 5 weight percent, preferably 0.01 to 2.5 weight percent, more preferably zero to less than 1.5 weight percent, more preferably 0.05 to less than 2.5 weight percent.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, alkoxysulfolanes (C₁₀ alcohol, for example), aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of about 0.01 to 3 weight percent, preferably about 0.01 to 2 weight percent.

Antifoam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 weight percent and often less than 0.1 weight percent.

Inhibitors and Antirust Additives

Antirust additives (or corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. A wide variety of these are commercially available.

One type of antirust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of antirust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Yet another type of antirust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure.

Illustrative friction modifiers may include, for example, organometallic compounds or materials, or mixtures thereof. Illustrative organometallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like, and mixtures thereof. Similar tungsten based compounds may be preferable.

Other illustrative friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, alkoxylated fatty acid esters, alkanolamides, polyol fatty acid esters, borated glycerol fatty acid esters, fatty alcohol ethers, and mixtures thereof.

Illustrative alkoxylated fatty acid esters include, for example, polyoxyethylene stearate, fatty acid polyglycol ester, and the like. These can include polyoxypropylene stearate, polyoxybutylene stearate, polyoxyethylene isosterate, polyoxypropylene isostearate, polyoxyethylene palmitate, and the like.

Illustrative alkanolamides include, for example, lauric acid diethylalkanolamide, palmic acid diethylalkanolamide, and the like. These can include oleic acid diethyalkanolamide, stearic acid diethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylated hydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.

Illustrative polyol fatty acid esters include, for example, glycerol mono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerol mono-stearate, and the like. These can include polyol esters, hydroxyl-containing polyol esters, and the like.

Illustrative borated glycerol fatty acid esters include, for example, borated glycerol mono-oleate, borated saturated mono-, di-, and tri-glyceride esters, borated glycerol mono-stearate, and the like. In addition to glycerol polyols, these can include trimethylolpropane, pentaerythritol, sorbitan, and the like. These esters can be polyol monocarboxylate esters, polyol dicarboxylate esters, and on occasion polyoltricarboxylate esters. Preferred can be the glycerol mono-oleates, glycerol dioleates, glycerol trioleates, glycerol monostearates, glycerol distearates, and glycerol tristearates and the corresponding glycerol monopalmitates, glycerol dipalmitates, and glycerol tripalmitates, and the respective isostearates, linoleates, and the like. On occasion the glycerol esters can be preferred as well as mixtures containing any of these. Ethoxylated, propoxylated, butoxylated fatty acid esters of polyols, especially using glycerol as underlying polyol can be preferred.

Illustrative fatty alcohol ethers include, for example, stearyl ether, myristyl ether, and the like. Alcohols, including those that have carbon numbers from C=3 to C=50, can be ethoxylated, propoxylate, or butoxylated to form the corresponding fatty alkyl ethers. The underlying alcohol portion can preferably be stearyl, myristyl, C11-C13 hydrocarbon, oleyl, isosteryl, and the like.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 5 weight percent, or about 0.1 weight percent to about 2.5 weight percent, or about 0.1 weight percent to about 1.5 weight percent, or about 0.1 weight percent to about 1 weight percent. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 25 ppm to 700 ppm or more, and often with a preferred range of 50-200 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table 1 below.

It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. Accordingly, the weight amounts in the table below, as well as other amounts mentioned herein, are directed to the amount of active ingredient (that is the non-diluent portion of the ingredient). The weight percent (wt %) indicated below is based on the total weight of the lubricating oil composition.

TABLE 1 Typical Amounts of Other Lubricating Oil Components Approximate Approximate wt % wt % Compound (Useful) (Preferred) Dispersant 0.1-20  0.1-8   Detergent 0.1-20  0.1-8   Friction Modifier 0.01-5   0.01-1.5  Antioxidant 0.1-5   0.1-1.5 Pour Point Depressant 0.0-5   0.01-1.5  (PPD) Anti-foam Agent 0.001-3    0.001-0.15  Viscosity Index Improver 0.1-2   0.1-1   (solid polymer basis) Anti-wear 0.2-2.0 0.4-1.2 Inhibitor and Antirust 0.01-5   0.01-1.5 

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of lubricant oil additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The following non-limiting examples are provided to illustrate the disclosure.

EXAMPLES

Formulations were prepared as described in FIG. 1. All of the ingredients used herein are commercially available. Group I and Group II base stocks were used in the formulations. In FIG. 1, the total treat rate may not add up to 100% due to rounding.

The detergents used in the formulations were an overbased calcium phenate (Detergent 1), a carboxylate mixture of overbased and neutral basicity (Detergent 2), an overbased calcium salicylate (Detergent 3), a neutral calcium salicylate (Detergent 4), and a neutral calcium sulfonate (Detergent 5).

Other additives used in the formulations included an antioxidant, a pour point depressant, and a defoamant. The antioxidant used in the formulations was a diphenyl amine. The pour point depressant used in the formulations was a methacrylate polymer. The defoamant used in the formulations was a silicon-based defoamant.

The zinc dialkyl dithiophosphate (ZDDP) antiwear compounds having primary and/or secondary alkyl groups used in the formulations were a ZDDP having predominantly (i.e., greater than about 80 weight %) primary 2-ethyl-1-hexanol alkyl groups (ZDDP 1), a ZDDP having predominantly (i.e., greater than about 80 weight %) secondary 2-butanol and 4-methyl-2-pentanol alkyl groups (ZDDP 2), a ZDDP having mixed (i.e., between about 20 weight % to about 80 weight %) primary 2-ethyl-1-hexanol and secondary 2-butanol alkyl groups (ZDDP 3), a ZDDP having predominantly (i.e., greater than about 80 weight %) secondary 4-methyl-2-pentanol and 2-propanol alkyl groups (ZDDP 4), a ZDDP having predominantly (i.e., greater than about 80 weight %) secondary 4-methyl-2-pentanol and 2-propanol alkyl groups (ZDDP 5), a ZDDP having predominantly (i.e., greater than about 80 weight %) primary 1-isobutanol and 2-ethyl-1-hexanol alkyl groups (ZDDP 6), and a ZDDP having predominantly (i.e., greater than about 80 weight %) secondary 4-methyl-2-pentanol alkyl groups (ZDDP 7).

Testing was conducted for formulations described in FIG. 1. Testing included kinematic viscosity (KV) at 100° C. measured by ASTM D445, elemental analysis of lubricating oils measured by ASTM D4951, antiwear of the lubricating oils measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG (i.e., FZG Failure Load Stage determined by observing gears at increasing load levels until scuffing is noticed on the gear face), and demulsibility of the lubricating oils measured by High Shear Demulsibility Test, where oil is mixed with a minor amount of water in a high shear blending environment to generate an emulsion, then centrifuged and rated for emulsion layer, free water, water in oil, oil layer description and water.

Examples 1 and 2 unexpectedly retain FZG performance relative to the comparative examples. Desired FZG results are a fail stage 12. Examples 1 and 2 also show unexpected demulsibility results with low emulsion performance, which is desired, relative to the comparative examples, with better emulsion layer, free water, and water in oil results. A lower result for emulsion, preferably below 1 mL, and lower water in oil, preferably below 1 wt % is desirable, while a higher result for free water, preferably above 3.8 mL, is preferred. Other comparative examples are unable to achieve desired demulsibility performance in all four test parameters at higher ZDDP treat rates, while Examples 1 and 2 are able to do so. The results of such testing are set forth in FIG. 1.

Additional formulations were prepared as described in FIGS. 2A and 2B. All of the ingredients used herein are commercially available. Group I and II base stocks were used in the formulations. The detergents used in the formulations were an overbased calcium phenate and a neutral calcium sulfonate. The antioxidant used in the formulations was a diphenyl amine. A methacrylate polymer pour point depressant and a silicon-based defoamant were used in the formulations. The ZDDP compound, and concentration of the ZDDP compound in the formulations, were varied in order to determine the effect of different ZDDP compounds having different primary and secondary alkyl groups, and also to determine the effect of the ZDDP concentration in the lubricating oils.

In addition to ZDDP compounds used in the formulations set forth in FIG. 1, other ZDDP compounds were used in these formulations that included a ZDDP having predominantly (i.e., greater than about 80 weight %) primary 1-isobutanol and 1-pentanol alkyl groups (ZDDP 8), a ZDDP having predominantly (i.e., greater than about 80 weight %) primary 2-ethyl-1-hexanol alkyl groups (ZDDP 9), a ZDDP having mixed (i.e., between about 20 weight % to about 80 weight %) secondary 2-propanol and 2-butanol and primary 2-ethyl-1-hexanol alkyl groups (ZDDP 10), and a ZDDP having predominantly (i.e., greater than about 80 weight %) secondary 2-propanol and 4-methyl-2-pentanol alkyl groups (ZDDP 11).

FIGS. 2A and 2B detail which ZDDP was used in each of the examples given in FIGS. 3-19. The general formula used in all examples in FIGS. 3-19 is approximately 96-97 weight % base oil, approximately 0-1 weight % ZDDP, and approximately 3% other additives. The only varying component is the ZDDP for both FIGS. 2A and 2B. FIG. 2B also shows the ratio of primary to secondary ZDDP in each test.

Testing was conducted for these formulations. The testing included antiwear of the lubricating oil measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG (i.e., FZG Failure Load Stage determined by observing gears at increasing load levels until scuffing is noticed on the gear face), and demulsibility of the lubricating oil measured by High Shear Demulsibility Test where oil is mixed with a minor amount of water in a high shear blending environment to generate an emulsion, then centrifuged and rated for emulsion layer, free water, water in oil, oil layer description and water. Emulsion and water in oil were plotted. Lower numbers in these fields indicate superior demulsibility performance.

FIG. 3 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol. The ZDDP alcohol composition showed an unexpected amount of ZDDP additive exists about 0.4 weight %, after which free water and emulsion performance suffered. Even low ZDDP treat improved demulsibility over ZDDP-free reference (Blend A.0).

FIG. 4 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol. Low amounts of ZDDP around 0.2 weight % showed unexpectedly favorable improvement in free water, emulsion, and water in oil. Demulsibility performance plateaued at a relatively low level. Positive performance was observed for ZDDP having alkyl groups derived from mostly 4-methyl-2-pentanol.

FIG. 5 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-propanol (i-C3), 2-butanol (2-C4), and 2-ethyl-1-hexanol. Low amounts of ZDDP, about 0.4 weight %, provided an unexpected improvement. More ZDDP is added to the system to provide demulsibility improvement.

FIG. 6 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-butanol. Low amounts of ZDDP, about 0.4 weight %, provided an unexpected improvement in all three parameters of the high shear demulsibility test. More ZDDP added in the system provided additional improvement. Shorter alcohol chains were less effective for demulsibility compared to longer alcohol chains of over about 6 carbon atoms per alcohol group.

FIG. 7 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 1-isobutanol and 1-pentanol. Low amounts of ZDDP around 0.4 weight % provided an unexpected improvement. More ZDDP added in the system provided additional improvement.

FIG. 8 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, and 2-butanol. An unexpected rapid initial demulsibility benefit was observed with about 0.2 weight percent ZDDP containing mostly 2-ethyl-1-hexanol. Additional ZDDP treat did not provide any additional benefit for demulsibility, in fact performance was worse.

FIG. 9 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, and 2-butanol. An unexpected rapid initial demulsibility benefit was observed with about 0.2 weight % ZDDP containing mixed 2-ethyl-1-hexanol and 2-propanol. The 2-ethyl-1-hexanol ZDDP portion is the dominant component and improves demulsibility performance to superior levels in this blend. Higher treat rates degraded demulsibility performance.

FIG. 10 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 1-butanol, and 1-pentanol. Rapid initial demulsibility benefit was unexpectedly observed with ZDDP containing 2-ethyl-1-hexanol at about 0.2 weight % treat rate. Higher treat rates degraded demulsibility performance.

FIG. 11 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-butanol. Unexpectedly, no initial water-in-oil demulsibility benefit was observed when 2-propanol and 2-butanol were the major component at ZDDP levels around 0.2 weight %. Additional ZDDP, around 0.5 weight % to 0.8 weight %, was needed for the 4-methyl-2-pentanol component to become effective.

FIG. 12 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-butanol. An initial demulsibility benefit was unexpectedly observed when about 0.2 weight % of this mixed ZDDP was present at this ratio. Demulsibility performance did not deteriorate with increased treat rate over the range tested.

FIG. 13 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-butanol. A rapid initial demulsibility benefit was observed when 4-methyl-2-pentanol was the primary ZDDP component at ZDDP levels of about 3000 ppm of the ZDDP mixture as a total of the entire formulation. Demulsibility performance did not deteriorate with increased treat rate over the range tested.

FIG. 14 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, and 2-butanol. The total treat rate was 0.6 wt % ZDDP additive with varying ratio of the specific alcohol chains. As the ratio shifted from mostly 2-propanol and 2-butanol to mostly 2-ethyl-1-hexanol, emulsion and free water became poorer. An unexpected benefit was observed at ratios in the middle of this range, using a combination of both ZDDP types in the oil.

FIG. 15 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, and 2-butanol. The total treat rate was 0.4 wt % with varying ratio. As the ratio shifted from mostly 2-propanol and 2-butanol to mostly 2-ethyl-1-hexanol, emulsion and free water became poorer. An unexpected benefit was observed at ratios in the middle of this range, using a combination of both ZDDP types in the oil.

FIG. 16 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, 2-butanol, and 2-ethyl-1-hexanol. The total treat rate was 0.6 wt % with varying ratio. All ratios provided an unexpected benefit over oil without ZDDP.

FIG. 17 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, 2-butanol, and 2-ethyl-1-hexanol. The total treat rate was 0.4 wt % with varying ratio. All ratios provided a benefit over oil without ZDDP.

FIG. 18 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples showing unexpected demulsibility results at differing antiwear levels. All ratios provide a benefit over oil without ZDDP. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-butanol.

FIG. 19 graphically shows the results of demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., emulsion layer and water in oil) in accordance with the Examples showing unexpected demulsibility results at differing antiwear levels. All ratios provide a benefit over oil without ZDDP. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-butanol.

FIG. 20 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, and 2-butanol. A beneficial ZDDP treat level containing this mixture of alcohols exists around 0.25 weight percent.

FIG. 21 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, 2-butanol, and 4-methyl-2-pentanol. Increasing 2-butanol and/or 4-methyl-2-pentanol provided improved FZG and demulsibility. Increased 2-ethyl-1-hexanol led to poorer FZG but improved demulsibility.

FIG. 22 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 4-methyl-2-pentanol, 2-propanol, and 2-ethyl-1-hexanol. Increasing 4-methyl-2-pentanol provided improved demulsibility but no FZG benefit.

FIG. 23 graphically shows the results of antiwear testing of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, and demulsibility testing of the lubricating oil measured by High Shear Demulsibility Test (i.e., water in oil) in accordance with the Examples. The alkyl groups of the zinc dialkyl dithiophosphate compound are derived from 2-ethyl-1-hexanol, 2-propanol, 2-butanol, and 4-methyl-2-pentanol. Increasing 4-methyl-2-pentanol and 2-ethyl-1-hexanol type ZDDP improved FZG performance and maintained excellent demulsibility performance.

PCT and EP Clauses:

1. A method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and an antiwear additive as a minor component; wherein the antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula

Zn[SP(S)(OR¹)(OR²)]₂

wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups; and wherein the R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups.

2. The method of clause 1 wherein the lubricating oil base stock comprises a Group I or Group II base oil.

3. The method of clauses 1 and 2 wherein, the primary or secondary C₁ to C₈ alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-hexanol, and mixtures thereof.

4. The method of clauses 1-3 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, is present in an amount of from 0.1 weight percent to 1.2 weight percent, based on the total weight of the lubricating oil; or wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil; or wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil; or wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, is present in an amount of from 0.3 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil.

5. The method of clauses 1-4 wherein the lubricating oil is a marine lubricating oil.

6. The method of clauses 1-5 wherein the lubricating oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.

7. The method of clauses 1-6 wherein, in antiwear measurements of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance of the lubricating oil is improved as compared to the antiwear performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups; and wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the demulsibility performance is improved as compared to the demulsibility performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups.

8. A lubricating engine oil having a composition comprising a lubricating oil base stock as a major component; and an antiwear additive as a minor component; wherein the antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula

Zn[SP(S)(OR¹)(OR²)]₂

wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups; and wherein the R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil, are sufficient for the lubricating engine oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups.

9. The lubricating engine oil of clause 8 wherein the lubricating oil base stock comprises a Group I or Group II base oil.

10. The lubricating engine oil of clauses 8 and 9 wherein, the primary or secondary C₁ to C₈ alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-hexanol, and mixtures thereof.

11. The lubricating engine oil of clauses 8-10 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, is present in an amount of from 0.1 weight percent to 1.2 weight percent, based on the total weight of the lubricating oil; or wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil; or wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil; or wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, is present in an amount of from 0.3 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil.

12. The lubricating engine oil of clauses 8-11 wherein the lubricating engine oil is a marine lubricating oil.

13. The lubricating engine oil of clauses 8-12 wherein the lubricating engine oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.

14. The lubricating engine oil of clauses 8-13 wherein, in antiwear measurements of the lubricating engine oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance of the lubricating engine oil is improved as compared to the antiwear performance of a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups; and wherein, in demulsibility measurements of the lubricating engine oil as measured by High Shear Demulsibility Test, the demulsibility performance is improved as compared to the demulsibility performance of a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups.

15. A gear component of a marine engine lubricated with the lubricating engine oil of clauses 8-14.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims 

What is claimed is:
 1. A method for improving antiwear performance and demulsibility performance in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising a lubricating oil base stock as a major component; and an antiwear additive as a minor component; wherein the antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula Zn[SP(S)(OR¹)(OR²)]₂ wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups; and wherein the R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil, are sufficient for the lubricating oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil.
 2. The method of claim 1 wherein the lubricating oil base stock comprises a Group I or Group II base oil.
 3. The method of claim 1 wherein the primary or secondary C₁ to C₈ alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-hexanol, and mixtures thereof.
 4. The method of claim 1 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, is present in an amount of from 0.1 weight percent to 1.2 weight percent, based on the total weight of the lubricating oil.
 5. The method of claim 1 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil.
 6. The method of claim 1 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil.
 7. The method of claim 1 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, is present in an amount of from 0.3 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil.
 8. The method of claim 1 wherein the lubricating oil is a marine lubricating oil.
 9. The method of claim 1 wherein, in antiwear measurements of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the lubricating oil achieves at least a FZG Failure Load Stage 11 or 12 rating.
 10. The method of claim 1 wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the lubricating oil achieves at least 3.8 mL free water, less than 1 mL emulsion, and less than 1 weight percent water in oil.
 11. The method of claim 1 wherein the lubricating oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.
 12. The method of claim 1 wherein, in antiwear measurements of the lubricating oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance of the lubricating oil is improved as compared to the antiwear performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil; and wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the demulsibility performance is improved as compared to the demulsibility performance of a lubricating oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating oil.
 13. A lubricating engine oil having a composition comprising a lubricating oil base stock as a major component; and an antiwear additive as a minor component; wherein the antiwear additive comprises a zinc dialkyl dithiophosphate compound represented by the formula Zn[SP(S)(OR¹)(OR²)]₂ wherein R¹ and R² are independently primary or secondary C₁ to C₈ alkyl groups; and wherein the R¹ and R² primary or secondary alkyl groups of the zinc dialkyl dithiophosphate compound, and the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil, are sufficient for the lubricating engine oil to exhibit improved antiwear performance and demulsibility performance as compared to antiwear performance and demulsibility performance achieved using a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil.
 14. The lubricating engine oil of claim 13 wherein the lubricating oil base stock comprises a Group I or Group II base oil.
 15. The lubricating engine oil of claim 13 wherein the primary or secondary C₁ to C₈ alkyl groups of the zinc dialkyl dithiophosphate compound are derived from an alcohol selected from the group consisting of: 2-propanol, 1-butanol, 1-isobutanol, 2-butanol, 1-pentanol, 3-methyl-1-butanol, 2-pentanol, 3-pentanol, 3-methyl-2-butanol, 1-hexanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, and 2-ethyl-1-hexanol, and mixtures thereof.
 16. The lubricating engine oil of claim 13 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, is present in an amount of from 0.1 weight percent to 1.2 weight percent, based on the total weight of the lubricating engine oil.
 17. The lubricating engine oil of claim 13 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-ethyl-1-hexanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil.
 18. The lubricating engine oil of claim 13 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 4-methyl-2-pentanol, is present in an amount of from 0.1 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil.
 19. The lubricating engine oil of claim 13 wherein the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, in which the R¹ and R² primary or secondary alkyl groups are derived from 2-propanol, 2-butanol, 1-iso-butanol, or n-pentanol, is present in an amount of from 0.3 weight percent to 0.8 weight percent, based on the total weight of the lubricating engine oil.
 20. The lubricating engine oil of claim 13 wherein the lubricating engine oil is a marine lubricating oil.
 21. The lubricating engine oil of claim 13 wherein, in antiwear measurements of the lubricating engine oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the lubricating engine oil achieves at least a FZG Failure Load Stage 11 or 12 rating.
 22. The lubricating engine oil of claim 13 wherein, in demulsibility measurements of the lubricating oil as measured by High Shear Demulsibility Test, the lubricating oil achieves at least 3.8 mL free water, less than 1 mL emulsion, and less than 1 weight percent water in oil.
 23. The lubricating engine oil of claim 13 wherein the lubricating engine oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.
 24. The lubricating engine oil of claim 13 wherein, in antiwear measurements of the lubricating engine oil as measured by relative scuffing load carrying capacity test method ISO 14635-1 FZG, the antiwear performance of the lubricating engine oil is improved as compared to the antiwear performance of a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil; and wherein, in demulsibility measurements of the lubricating engine oil as measured by High Shear Demulsibility Test, the demulsibility performance is improved as compared to the demulsibility performance of a lubricating engine oil containing a minor component other than the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups, and in an amount other than the amount of the zinc dialkyl dithiophosphate compound having the R¹ and R² primary or secondary alkyl groups in the lubricating engine oil.
 25. A gear component of a marine engine lubricated with the lubricating engine oil of claim
 13. 